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Friday, December 18, 2009

Clinical note

In vasogenic edema,(typically secondary to a brain tumor), the blood vessel are poorly developed, are leaky, and lack the transport properties of a normal BBB. This abnormal vessel permeability results in accumulation of interstitial fluid in the brain. Permeablity of the BBB can also be altered in infections such as bacterial meningitis; although this accounts for some of the adverse neurologic effects of infection, it also permits improved delivery antibiotics to the CNS.

Prof. Noriah's note (4)


Picture's source: http://www.stanford.edu/

Characteristic of CNS
Protected by cranium, meningis + csf

CSF
-secreted by choroid plexuses (special capillaries in ventricles of the brain → form BBB)
-act as shock absorbing medium

Brain stem
-midbrain
-pons → resp. center
-medulla → resp. center, cardiac center (coordinating reflex for vomiting, swallowing, coughing, sneezing)
-cerebellum → required for smooth coordinated movement + equilibrium

Blood brain barrier (BBB)
-Composed of endothelial cells packed tightly together to form tight junction that prevent passage of most molecules.
-An underlying basement membrane and specialized glial cells (astrocyte), which projects processes (pedicles) that attach to the walls of the capillary, reinforce this barrier.
-Very few substances can cross the BBB into brain tissue:
(1)Water is able to freely diffuse
(2)Glucose (the primary energy source of the brain) and amino acid require carrier-mediated transport
(3)Nonpolar lipid soluble substances can cross more readily than polar water-soluble ones
(4)Other active transport systems are present to pump weak organic acids, halides and extracellular K+ across the BBB

The blood – CSF barrier
-Cerebrospinal fluid (CSF) is clear, colorless fluid that normally contains none or few cells, a small amount of protein, and a moderate amount of glucose
-The blood – CSF barrier is composed of epithelial cells of the choroid plexus – a highly vascular structure, located within the ventricles .

Function of NS
Detect changes in internal and external environmental (in + outside the body)
via sense organs (receptors)

↓ (information sent to CNS by sensory nerve/afferent nerve)

CNS (brain/spinal cord) – intergrating center

↓ (analyse the sensory information via motor nerve/efferent nerve – send instruction to)

Muscle/gland

*Receptor
(a) special receptor
- hearing
- smell
- taste
- chemoreceptor
- osmoreceptor

(b) general receptor
- pain
- temperature
- proprioreceptor

Thursday, December 17, 2009

Prof. Noriah's note (3)

C) CNS
Consist of brain + spinal cord
Protected by cranium + vertebral column
Meninges + cerebrospinal fluid (csf)

Meninges:
3 layers
-dura mater
-arachroid + pia mater (form subarachroid space filled with CSF)

CSF
-secreted by choroid plexuses (CP)
-CP is a specialized capillaries located on the root of each ventricles
-CP produces CSF, secretes + filter harmful material, → form BBB (blood brain barrier)
-CSF circulate round the brain + spinal cord → enters superior sagittal sinus (venous sinuses) → jugular vein → superior vena cava

Function of CSF
-Protect the brain + spinal cord from banging / contact injury against the inner wall of cranium + wall of vertebral canal (shock absorbing medium)

Friday, December 11, 2009

Prof. Noriah's note (2)

Spinal cord

Note:

Tract: is a bundle of myelinated nerve fibers located in the CNS (brain + spinal cord).

Sensory (ascending tract) consist of fibers that carry impulse up the spinal cord to different region of the brain.

Motor (descending) tracts - nerve fibers that carry impulses down the spinal cord.


Pathway: is the route followed by a nerve impulse as it travel through the nervous system

In sensory pathway:
Sensory receptor → sensory neuron into spinal cord → travels up the spinal cord by way of sensory (ascending) tract → brain

In motor pathway:
Impulse starts in the brain → travel down the spinal cord by motor (descending) tract → exit spinal cord by way of motor nerve → ends of a muscle/gland

Prof. Noriah's note

Nervous system:
1. CNS
2. PNS


CNS

- consist of brain + spinal cord


PNS

- consist of nerves outside the brain and spinal cord

- cranial nerve (12 pairs) - emerging from the brain - mainly supply structure above the neck

- spinal nerve (31 pairs) - emerging from the brain - supply structures in the trunk + limb


Note: Neuron
- afferent (sensory) = carry impulses towards CNS
- efferent (motor) = carry impulse away from CNS
- interneuron = reside entirely within CNS


Efferent nerve
- 2 types
(a) Somatic nerve (motor nerve) - innervate skeletal muscle(somatic nervous system)

(b) Autonomic nerve (motor nerve) - innervate cardiac muscle, smooth muscle or glands (Autonomic Nervous System - ANS)

Action carried out by somatic nervous system are voluntary.

Action carried out by ANS are involuntary + automatic


Sensory Neuron
Carry impulse into CNS from receptors.

Receptors
- for general senses (touch, pressure, vibration, temperature, pain + proprioceptor)

- for special senses ( smell, taste, vision, hearing + equilibrium)